Seal bars are commonly used in the flexible packaging industry to cut and seal plastic films around articles such as food products. Known seal bars of which I am aware generally comprise a pair of seal bar halves which are machined from metal bar stock to a desired shape and then drilled and fastened together with screws. A cutting knife is mounted with screws between the halves. The knife edge projects from lengthwise edges of the halves which are sealing surfaces. A heating element clamped between the halves is connected to a power source to heat the knife and sealing surfaces.
In use, the seal bar which is pivotally mounted to a machine frame of a wrapping machine, descends into contact with a continuous ribbon of plastic film which has been wrapped around and extends between adjacent articles being packaged in a known manner. The action of heat and cutting severs the film between the packages while the heated sealing surfaces fuse the film together on either side of the cutting knife to seal the package along one or more edges.
Various disadvantages occur with the aforementioned seal bars. For example, machining the of the seal bar halves is relatively expensive and limits the halves and thereby the seal bar to conventional straight seal bar shapes. In addition, extremely close tolerances are required to ensure that the various components can be properly secured together with screws. The overall manufacture and assembly of the individual components is time consuming and labor extensive, thereby increasing costs.
It is accordingly one object of the present invention to simplify the manufacture and assembly of seal bars.
Another object to manufacture seal bar halves using manufacturing methods hitherto unknown in the art of seal bar assembly and which enables the seal bar halves and thereby the seal bar to be formed in unconventional shapes to suit the particular geometry of the products being wrapped.
Still another object is to eliminate the need for close tolerances in the manufacture and assembly of the various components forming the seal bar.
A further object is to assemble components of the seal bar together without screws.